Took mine off yesterday & it was packed solid at the fitting where the sensor screws in & the sensor itself was packed. Started truck with sensor removed & felt very little if any pressure out of the tube. Took the tube off & cleaned it with brake kleen & weedwacker line, it wasn't too bad & the fitting into the exhaust manifold was clear. The fitting that the tube & sensor connect to was a pia started with a piece of wire then twisted drill bits with my fingers through the sh!t. After I reconnected the tube started engine & had plenty of pressure, put new sensor back & I hope my mpg's come back.
I'm glad I went ahead & got a new sensor because I really don't think I could have gotten the soot out of the old one w/o screwing it up. I don't know how much digging around in there the sensor could stand.